Evaluation of Efficiency of Polymerization, Surface Roughness, Porosity and Adaptation of Flowable and Sculptable Bulk Fill Composite Resins.

Elizabeta Gjorgievska,Dragana Gabric,Daewon Haam,Daniel S Oh,Nichola J Coleman

doi:10.3390/molecules26175202

Abstract

A new category of commercial bulk fill composite resins (CRs) enables the placement of 4-mm-thick layers as an alternative to the traditional time-consuming incremental technique. The purpose of the present study was to compare the efficiency of the polymerization, adaptation and porosity of two high-viscosity ‘sculptable’ bulk fill CRs (Filtek™ Bulk Fill (3M™ ESPE, St. Paul, MN, USA) and Tetric EvoCeram® Bulk Fill (Ivoclar Vivadent AG, Schwan, Liechtenstein)) and two low-viscosity ‘flowable’ bulk fill CRs (SureFil® SDR™ flow (Dentsply Sirona, Charlotte, NC, USA) and Tetric EvoFlow® Bulk Fill (Ivoclar Vivadent AG, Schaan, Liechtenstein)). Cylindrical samples of the bulk fill CRs (4 mm height × 10 mm diameter) were analyzed by Fourier-transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). Additionally, occlusal cavities were prepared in twelve extracted human molars and restored with the bulk fill CRs (n = 3 for each CR). The adaptation and porosity of the bulk fill CRs were evaluated by X-ray microcomputed tomography (µCT) with a 3D morphometric analysis, and the adaptation was also analyzed by scanning electron microscopy (SEM) on longitudinal vestibulo-oral sections of the restored teeth. The AFM analysis demonstrated that the surface roughness of the SureFil® SDR™ flow was higher than that of the Tetric EvoFlow® Bulk Fill and that the surface roughness of Filtek™ Bulk Fill was higher than that of Tetric EvoCeram® Bulk Fill. µCT and SEM confirmed that the flowable bulk fill CRs had excellent adaptation to the cavity walls. The 3D morphometric analysis showed the highest and lowest degrees of porosity in Filtek™ Bulk Fill and Tetric EvoFlow® Bulk Fill, respectively. In general, the flowable bulk fill CRs exhibited better adaptation, a higher efficiency of polymerization and lower porosity than the sculptable materials.

Highlights

The main disadvantages of composite resins (CRs) are their moisture sensitivity and polymerization shrinkage, which lead to the contraction of the total composite volume and the development of polymerization stress [1,2]
The efficiency of polymerization between the top and the bottom layers for each bulk fill CR was estimated by comparing the ratios of the intensities of the Fourier-transform infrared spectroscopy (FTIR) peaks for the reactive polymerizing C=C bond and the invariant C=O bond in the cured polymer and monomer (Table 2)
The lowest value of 78.07 ± 1.46% was recorded for Tetric EvoCeram® Bulk Fill (Ivoclar Vivadent AG, Schaan, Liechtenstein), this was not statistically different from that of the other sculptable CR at 80.87% ± 2.05%, FiltekTM Bulk Fill

Summary

Introduction

The main disadvantages of composite resins (CRs) are their moisture sensitivity and polymerization shrinkage, which lead to the contraction of the total composite volume and the development of polymerization stress [1,2]. The negative effects of polymerization stress (e.g., cusp deflection, marginal gap and dentinal defect formation) can be minimized by using multiple layering techniques and different methods of light polymerization [3]. The first is to use a ‘sculptable’ high-viscosity bulk fill restorative in a single increment in cavity preparations up to 4 mm deep, and the second is to apply a ‘flowable’ low-viscosity resin as a base material for dentin replacement in a single increment, which is finished with a final layer of conventional CR to restore the enamel

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Conclusion